Semiconductor internal combustion engine ignition system



y 4, 1966 R. L. KONOPA 3,253,163

SEMICONDUCTOR INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed Dec. 20,1963 INVENTOR RICHARD L. KONOPA BY (1 ARM Hi5 ATTOBN EY United StatesPatent 3,253,163 SEMICGNDUCTOR INTERNAL COMBUSTION ENGINE IGNTTIONSYSTEM Richard L. Konopa, Anderson, Ind., assignor to General MotorsCorporation, Detroit, Mich, a corporation of Delaware Filed Dec. 20,1963, Ser. No. 332,012 9 Claims. (Cl. 307-885) This invention relates toa semiconductor internal combustion engine ignition system and moreparticularly to an ignition system that uses a unijunction transistor asan active element in the ignition system.

The ignition system to be described is in some respects similar to theignition ssytems shown in the Konopa Patent 3,087,090, and in the Shortet al. Patent 3,087,001.

The above-mentioned Konopa and Short, et al. patents disclosesemiconductor ignition systems wherein a transistor controls primarywinding current. In these systems, resistor-capacitor coupling is usedbetween certain transistor stages. Although the systems illustrated inShort, et a1. and Konopa perform satisfactorily, it has been found thatimproved low-speed triggering can be achieved if the triggering of thesystem can be made independent of the rate of change of magnetic pick-upvoltage.

It accordingly is one of the objects of this invention to provide asemiconductor ignition system wherein improved triggering of the systemis achieved at low engine speeds.

Another object of this invention is to provide a semiconductor ignitionsystem wherein the amount of voltage required to trigger the system isdecreased as compared to known systems.

Still another object of this invention is to provide a transistorignition system which includes a plurality of transistors and wherein atleast one of these transistors is a unijunction transistor.

Another object of this invention is to provide a transistor ignitionsystem of the breakerless type which uses a plurality of transistors oneof which is a unijunction transistor.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

The single figure drawing is a schematic circuit diagram of an ignitionsystem made in accordance with this invention.

Referring now to the drawing, the reference numeral 10 designates aninternal combustion engine having a plurality of spark plugs 12. Thespark plugs are connected with conductors 14 which in turn are connectedwith the electrodes or inserts 16 of a distributor cap 18. Theelectrodes 16 are insulated from each other by the insulating materialof the distributor cap and these electrodes or inserts cooperate with arotor contact 20 which is driven by the engine 10 and which serves todistribute spark energy to the electrodes 16 from a conductor 22.

The source of direct current for the ignition system takes the form of abattery 24, one side of which is grounded. The opposite side of thebattery is connected with an ignition switch 26 and 'when switch 26 isclosed, battery voltage is applied across power supply conductors 28 and30. It will be appreciated that on a motor vehicle, the conductors 28and 30 can also be supplied by a generator which has a direct currentoutput.

The control mechanism for controlling ignition firing is a magneticpick-up generally designated by reference numeral 32. This magneticpick-up has a rotor 34 that is formed of magnetic material. The rotor 34and the rotor contact 20 are synchronized in their rotation and are bothdriven by the engine 10.

3,253,163- Patented May 24, 1966 The rotor 34 has four arms which rotaterelative to a U-shaped part 36 which is formed of magnetic material. Apick-up coil 38 is wound on one leg of the U-shaped part and a permanentmagnet 40 is provided for causing a flowing of magnetic flux through theU-shaped part when the pole tips of the rotor 34 are aligned with theends of the U-shaped part. 'It will be appreciated that as the rotor 34rotates, pulses of voltage are induced in the pick-up coil 38 which havea predetermined spacing. The frequency of these pulses of voltagedepends upon the speed of rotation of the rotor 34 and therefore dependsupon engine speed. The pulses of voltage go positive and negative withperiods of no voltage output between the positive and negative pulses.

The ignition system has an NPN transistor 42. The base of transistor 42is connected with junction 44 located 'between pick-up coil 38 andresistor 46. The resistor 46 and the pick-up coil 38 are connected inseries across power conductors 28 and 30.

The emitter of transistor 42 is connected directly with groundedconductor 30 whereas the collector of transistor 42 is connected withjunction 48. A resistor 50 connects the junction 48 and the powerconductor 28.

The junction 48 is connected with the emitter of a unijunctiontransistor 52. This unijunction transistor has a base B and another baseB The base B of the unijunction transistor is connected with powerconductor 28. The base B of the unijunction transistor is connected withjunction 54 and this junction is conected to power conductor 30 by aresistor 56.

The unijunction transistor as is known to those skilled in the art, canbe formed from a silicon bar which has spaced ohmic contacts which areconnected with the base B and the base B The emitter electrode isconnected with a junction on the silicon bar. The characteristics ofthis transistor are such that the resistance between the emitter and thebase B decreases as the emitter current increases.

The junction 54 is connected with the base of an NPN transistor 58. Aresistor 60 connects the collector of transistor 58 with power conductor28. The emitter of transistor 58 is connected with junction 62. Aresistor 64 is connected between junction 62 and the grounded powerconductor 30.

The junction 62 is connected with the base of an NPN transistor 66. Theemitter of transistor 66 is connected to power conductor 30 while thecollector of transistor 66 is connected to one side of the primarywinding 68 of an ignition coil designated by reference numeral 70. Theopposite side of the primary winding 68 is connected with conductor 28at junction 74.

The secondary winding of the ignition transformer is designated byreference numeral 72. One side of this secondary winding is connectedwith junction 74 and therefore to one side of the primary winding 68.The opposite side of the secondary winding 72 is-connected to theconductor 22 to feed the spark plugs 12 via rotor contact 20, electrodes16, and spark plug leads 14.

When the ignition switch 26 is closed, the voltage of the direct currentsource 24 is impressed across conductors 28 and 30. If the engine 10 isnow being cranked by a starting motor or if it is running, the rotor 34will rotate and a train of voltage pulses will be induced in the pickupcoil 38.

When there is no voltage induced in the pick-up coil 38, the voltage atjunction 48 and on the emitter of unijunction transistor 52 is.sufiicient to cause the unijunction transistor 52 to conduct.Transistor 42 at this time is slightly conductive since its base isbiased positive with respect to its emitter by source 24 and the voltageat junction 48 is sufficiently positive to bias transistor 52 conductivedue to the voltage developed across slightly conductive transistor 42.With unijunction transistor 52 conductive, the junction 54 is positivewith respect to conductor 30 and transistor 58 is therefore biased to aconductive condition between its collector and emitter. Since transistor58 is conductive, the junction 62 will be positive with respect toconductor 30 and this applies .a forward bias to transistor 66 to switchit on between its collector and emitter. Since transistor 66 isconductive, current can flow from conductor 28, through primary winding68 and through the collector-emitter circuit of transistor 66 to thenegative grounded conductor 30.

To summarize, it is seen that with no voltage pulse induced in thepick-up coil 38, transistor 42 is slightly conductive and transistors52, 58 and 66 are all biased to a conductive condition.

When a voltage of the proper polarity is induced in pick-up coil 38, thebase of transistor 42 is driven more positive than its emitter and isdriven more positive than the bias it receives from battery 24 when novoltage is induced in pick-up coil 38. This increases the conduction oftransistor 42 in its collector-emitter circuit and the voltage dropacross resistor 50 tends to drive the junction 48 negative with respectto conductor 28. The voltage of junction 48 falls to a point where theunijunction transistor 52 now becomes nonconductive. When this happens,the voltage of junction 54 is reduced to a point where transistor 58becomes nonconductive in its collector-emitter circuit. When transistor58 goes nonconductive, the voltage of junction 62 approaches that ofconductor 30 and the transistor 66 is therefore now biased to anonconductive condition. When transistor 66 shuts pit in itscollector-emitter circuit, the primary circuit for the ignition systemis interrupted and current can no longer flow through primary winding68. As a result, a high voltage is induced in secondary winding 72 whichis applied to one of the spark plugs via conductor 22, rotor contact 20,one of the electrodes 16 .and then through one of the spark plug wires14. The rotor contact and rotor 34 are so synchronized in their rotationthat the high voltage is induced in secondary winding 72 at .a time thatthe rotor contact 20 is passing by one of the elecoutput voltagedeveloped in the coil 38. This is because when the transistor 42 is onlyslightly conductive or nonconductive, the voltage of junction 48 isincreased and approaches that of conductor 28 to bias transistor 52conductive. Whenever transistor 52 is conductive, the transistors 58 and66 are biased conductive as explained hereinbefore.

By using the unijunction transistor 52 and by eliminatingresistor-capacitor coupling, the low speed triggering of the ignitionsystem is improved and less voltage from coil 38 is required to triggerthe system as compared to systems that use resistor-capacitor coupling.

Although the ignition system as disclosed is to be used with a fourcylinder engine, it could be used with engines having a number ofcylinders other than four by changing the number of arms on rotor 34 andby changing the number of electrodes for distributor cap 18. The magnetic pick-up 32, the distributor cap 18 and the rotor contact 20 can bebuilt into one unit if so desired.

Transistors 42, 58 and 66 have all been shown as being of the NPN type.These transistors could be PNP transistors if desired.

While the embodiments of the present invention as herein disclosed,constitute .a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An ignition control circuit for an internal combustion engineignition system comprising, a magnetic pickup having an output coil, asource of direct current, a transistor having emitter, collector andbase electrodes,

means connecting the emitter and collector electrodes of said transistoracross said source of direct current, means connecting said output coilacross the emitter and base electrodes of said transistor, a unijunctiontransistor having an emitter, a first base and a second base, meansconnecting said first base and second base of said unijunctiontransistor across said source of direct current, an output circuitconnected with said unijunction transistor for controlling the currentflow through the primary winding of an ignition coil, and meansconnecting the emitter of said unijunction transistor with the collectorof said transistor.

2. A control circuit for controlling an internal combustion ignitionsystem comprising, a source of direct current, a magnetic pick-up havinga coil winding in which pulses of voltage are induced, an outputterminal adapted to control the primary circuit of an ignition system, atransistor having emitter, collector and base electrodes, meansconnecting the emitter and collector electrodes of said transistoracross said source of direct current, means connecting said output coilacross the emitter and base electrodes of said transistor, a unijunctiontransistor having first and second base electrodes and an emitterelectrode, means connecting said first and second base electrodes ofsaid unijunction transistor across said source of direct current, meansconnecting said output terminal with said unijunction transistor, andmeans connecting the emitter of said unijunction transistor with thecollector of said transistor.

3. A control circuit comprising, a source of direct current, aunijunction transistor having first and second base electrodes an anemitter electrode, a second transistor having emitter, collector andbase electrodes, a first circuit connected across said source of directcur-rent including said first and second base electrodes of saidunijunction transistor, an output terminal for said control circuitconnected with one of the base electrodes of said unijunctiontransistor, a second circuit connected across said source of directcurrent including a resistor and the emitter and collector electrodes ofsaid second transistor, means connecting the junction of said resistorand one of said emitter and collector electrodes of said transistor withthe emitter of said unijunction transistor, means connecting the baseelectrode of said transistor with said source of direct cur-rent in sucha manner that said transistor is normally biased at least partially onby said source of direct current, and a source of pulsating voltageconnected across the emitter and base electrodes of said transistor forperiodically driving the transistor fully conductive between its emitterand collector electrodes.

4. A control circuit for controlling an internal combustion engineignition system comprising, a source of direct current, a unijunctiontransistor having first and second base electrodes and an emitterelectrode, a transistor having emitter, collector and base electrodes, amagnetic pick-up having an output coil in which pulses of voltage areinduced, first, second and third parallel circuits connected across saidsource of direct current, said first circuit including a resistor andsaid output coil, said second circuit including the emitter andcollector electrodes of said transistor, said third circuit includingsaid first and second base electrodes of said unijunction transistor,means connecting the base electrode of said transistor between one sideof said resistor and said coil winding, and means connecting one of saidemitter and collector electrodes of said transistor with the emitter ofsaid unijunction transistor.

5. An ignition system for an internal combustion engine comprising, anignition coil having a primary winding and a secondary winding, a sourceof direct current, a first transistor having emitter, collector and baseelectrodes, means connecting the emitter and collector electrodes ofsaid first transistor and said primary winding in series across saidsource of direct current, a second transistor having emitter, collectorand base electrodes, means connecting the emitter and the collectorelectrodes of said second transistor across said source of directcurrent, means connecting the emitter electrode of said secondtransistor with base electrode of said first transistor, a unijunctiontransistor having first and second bases and an emitter, meansconnecting said first and second bases of said unijunction transistoracross said source of direct current, means connecting one of the basesof said unijunction transistor with the base of said second transistor,a third transistor having emitter, collector and base electrodes, meansconnecting the emitter and collector electrodes of said third transistoracross said source of direct current, means connecting the emitter ofsaid unijunction transistor with the collector of said third transistor,and timing means operated in synchronism with said engine forcontrolling the conduction of said third transistor.

6. The ignition system according to claim 5 wherein the timing means isa magnetic pick-up having an output coil connected across the emitterand base electrodes of said third transistor.

7. An ignition system for an internal combustion engine comprising, asource of direct current, an ignition coil having a primary winding anda secondary winding, a unijunction transistor having an input circuitand an output circuit, means connected with the output circuit of saidunijunction transistor for controlling current flow through said primarywinding of said ignition coil, a magnetic pick-up having an output coil,and means connecting said output coil with the input circuit of saidunijunction transistor, said unijunction transistor beng connectedacross said source of direct current, said source of direct currentfeeding the primary Winding of said ignition coil.

8. An ignition system for an internal combustion engine comprising, asource of direct current, an ignition coil having a primary winding anda secondary winding, a control circuit connected to said primary windingand with said source of direct current for controlling current flowthrough said primary winding, a timing circuit driven in synchronismwith said engine, a unijunction transistor having first and second basesconnected across said source of direct current and having an emitter,means connecting the emitter and one of the bases of said unijunctiontransistor with said timing circuit, and means connecting said one baseof said unijunction transistor with said control circuit.

9. An ignition system for an internal combustion engine comprising, asource of direct current, an ignition coil having a primary winding anda secondary winding, a control transistor, means connecting said controltransistor and said primary winding in series across said source ofdirect current, said control transistor switching on and off to controlprimary winding current, a voltage pulse generator having an outputcoil, and a circuit coupling said output coil and the emitter and baseelectrodes of said control transistor for applying control signals tosaid control transistor, said circuit including at least one unijunctiontransistor.

No references cited.

ARTHUR GAUSS, Primary Examiner.

J. BUSCH, Assistant Examiner.

1. AN IGNITION CONTROL CIRCUIT FOR AN INTERNAL COMBUSTION ENGINEIGNITION SYSTEM COMPRISING, A MAGNETIC PICKUP HAVING AN OUTPUT COIL, ASOURCE OF DIRECT CURRENT, A TRANSISTOR HAVING EMITTER, COLLECTOR ANDBASE ELECTRODES, MEANS CONNECTING THE EMITTER AND COLLECTOR ELECTRODESOF SAID TRANSISTOR ACROSS SAID SOURCE OF DIRECT CURRENT, MEANSCONNECTING SAID OUTPUT COIL ACROSS THE EMITTER AND BASE ELECTRODES OFSAID TRANSISTOR, A UNIJUNCTION TRANSISTOR HAVING AN EMITTER, A FIRSTBASE AND A SECOND BASE, MEANS CONNECTING SAID FIRST BASE AND SECOND BASEOF SAID UNIJUNCTION TRANSISTOR ACROSS SAID SOURCE OF DIRECT CURRENT, ANOUTPUT CIRCUIT CONNECTED WITH SAID UNIJUNCTION TRANSISTOR FORCONTROLLING THE CURRENT FLOW THROUGH THE PRIMARY WINDING OF AN IGNITIONCOIL, AND MEANS CONNECTING THE EMITTER OF SAID UNIJUNCTION TRANSISTORWITH THE COLLECTOR OF SAID TRANSISTOR.